1. Field
Embodiments of the disclosure relate to electronic devices, and more particularly, in one or more embodiments, to instrumentation amplifiers.
2. Description of the Related Technology
In some electronic systems, large DC offsets, which may also be referred to as the DC component of a signal, are present with relatively low-voltage data signals. The size of a “large” DC offset may vary from system to system. For example, in some systems, a 1000 millivolt (mV) offset is considered large, while in others, a 300 mV offset is considered large. Processing low-voltage signals in the presence of large DC offsets can be difficult. For example, when measuring small biopotential signals, relatively large differential DC offsets can appear due to respiration, muscular activity, and the like. In some cases, when measuring biopotential signals, the DC offset may be as high as 500 mV, while the biopotential signals themselves may be only a few mV.
In certain electronic measurement systems, amplifying biopotential signals with a large DC offset can cause significant problems. Amplifying the biopotential signals with a substantial gain may cause an amplifier of the system to saturate due to the large DC offset. Amplifying the biopotential signals with a relatively small gain may make it difficult to resolve the small biopotential signals, and lead to additional and more expensive filtering and gain stages later on. This problem is exacerbated in portable devices in which low supply voltages are used. Thus, a large DC offset makes it difficult to have high gain in the front-end of the measurement system.
Conventional solutions to this problem have involved low gain amplifier circuits to avoid saturating the system followed by a certain form of high pass filtering and additional gain stages. However, these solutions have resulted in additional signal filtering being performed by an expensive and slower digital signal processor (DSP), additional gain stages and filtering, expensive analog-to-digital (ADC) converters, and/or other circuit disadvantages.